This project will characterize variation in rates of aging in captive populations of vertebrates (mammals, birds, and reptiles) in zoological parks by quantifying the increase in mortality rate as a function of age, which is referred to as actuarial senescence (AS). Previous analyses have shown that AS in both natural and captive populations of mammals and birds varies by nearly an order of magnitude and that mortality resulting from aging processes is similar in natural and zoo settings. This suggests that aging-related mortality is the result of unique intrinsic causes of death (e.g., vascular disease, malignancies, autoimmune disease) rather than increasing vulnerability to extrinsic causes of mortality (predation, accident, contagious disease, weather- related starvation) owing to general deterioration of physiological function. Demographic patterns of aging will be compared by analyzing data in the International Species Information System (ISIS), which is the major international data base for zoos and animal parks. The data include ages and, in some cases, causes of death, as well as information about parentage that permit an assessment of inherited components of the rate of aging. After data editing, ages at death are converted to survival curves, which are then fit by a Weibull aging model to estimate the parameters of actuarial senescence for each species. Rate of AS will be related to other aspects of life history, including body mass, metabolic rate, development period, age at maturity, diet, and mortality rates in the wild. Ages at death will also be compared among siblings and half-siblings to estimate heritabilities of AS. The ultimate goals of this study are to establish a comparative data base for actuarial senescence in captive populations of vertebrates, to identify model organisms for further research on the physiology of aging, and to determine the feasibility of involving zoological institutions in collaborative, non-invasive research on aging.